154 MANUAL or BACTERIOLOGY. 



In this connection it is proper to refer to certain diseases due 

 to animal microorganisms. Malaria is conveyed from man to 

 man by mosquitoes of the genus Anopheles,* and is probably 

 transmitted exclusively in this manner. The parasite of malaria 

 undergoes part of its cycle of development in man, and another 

 part in the mosquito. Similarly, in Texas Fever, a disease of 

 cattle, it has been shown by Theobald Smith that the parasite 

 (a protozoon, Piroplasma) passes from cow to cow through the 

 cattle-tick (Bophilus annulatus or bovis).t In surra, a disease 

 chiefly affecting horses, and in the tsetse-fly disease of animals 

 the parasite (a protozoon, Trypanosoma) is transmitted by the 

 bites of flies, f It has recently been shown that the infectious 

 agent of yellow fever may be introduced into man by mosquitoes 

 of the genus Stegomyia. Under the administration of the 

 United States army yellow fever was suppressed in Havana 

 chiefly by measures intended to prevent the disease from being 

 carried by mosquitoes. Equally good results have since been 

 attained in controlling an epidemic of yellow fever at Laredo, 

 Texas, in 1903, |1 and a great reduction in the mortality at Rio 

 Janeiro, Brazil, has been effected. 



Auto-infection. — It is possible for the bacteria of disease 

 to be derived from the individual's own body — auto-infection. 

 The microbes of lobar pneumonia, for instance, flourish in the 

 mouths of a large number of people and under favoring circum- 

 stances may produce disease in the lungs or other parts. The 

 bacillus coli communis, which constantly inhabits the intestines, 

 may invade other organs and exhibit pathogenic properties 

 when the way is opened up for it by other disease processes. 



* For detail concerning mosquitoes consult the book of Dr. L. O. Howard. 

 McClure, Phillips & Co. 



fSee V. A. Moore. Infectious Diseases of Animals. 1902. 

 i Report on Surra. U. S. Bureau of Animal Industry. rgo2. 

 § Carroll. Journal American Medical Association. May 23, 1903. 

 II Guiteras. Journal American Medical Association. July 9, 1904. 



